a-sterno (better adst-), ĕre, v. a.,
to strew upon; hence, mid., to stretch one's self , to lie stretched : adsternunturque sepulchro, they prostrate themselves upon , Ov. M. 2, 343.
asternō (ad-st-) —, —, ere ad + sterno, to strew on (once): adsternuntur sepulcro, throw themselv...
An Elementary Latin Dictionary